The subject matter disclosed herein relates to lightning protection for aircraft and, more particularly, to a splined muff to provide for lightning protection for aircraft.
A ram air turbine (RAT) may be provided on an aircraft for multiple reasons. These include, but are not limited to, providing emergency power to the aircraft to enable a safe landing when normal power sources, such as the engines, are disabled. When operated, the RAT is deployed into an airstream proximate to an outer skin or wing of the aircraft. The airstream thus flows into the RAT and turns its rotor to generate electrical power.
Since it is often the case that the aircraft may fly near a thunderstorm during emergency events, lightning may strike the exposed RAT. Such lightning strikes can cause an electrical current to travel up the drivetrain of the RAT and is a well-known hazard and so every RAT design is tested to ensure that it can operate successfully after a lightning strike. As a result of this testing, it was found that while an air gap in a generator between the stator and the rotor needs to be small for the generator to operate efficiently, a small air gap can also allow lightning to arc between the rotor and stator and thus potentially disable the generator.
In addition, since many RAT designs include a hydraulic pump located downstream of the generator, the hydraulic pump can also be disabled by a lightning strike and an associated arc. In some cases, electrical current may damage the carbon face seal on the end of the pump to cause fluid loss.